The purpose of this research is to investigate the adaptive antibiotic resistance of the fungus Mucor. Although initially sensitive to the cycloheximide, trichodermin, and amphotericin B, Mucor will "adapt" to these antibiotics after several hours. This adaptation involves all the cells in the population, and does not result in the destruction of the inhibitors. Data show that adapted cells will modify C14-trichodermin, presumably producing inactive forms. This antibiotic adaptation will be investigated by studying: (1) mechanisms for the modification of antibiotics by adapted cells, and (2) subsidiary mechanisms, including the transport and sequestering of the drugs. These studies will be facilitated by the availability of mutants with altered responses to the three antibiotics. These mutants fall into two classes: constitutively resistant to antibiotics and super sensitive (i.e., no adaptive response).